Re: [PATCH v2] revision.c: fix possible null pointer access

From: Junio C Hamano <gitster@pobox.com>
Date: Dec 7, 2015, 20:31 UTC
Message-ID: <xmqqegeym25s.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <1449329244-4585-1-git-send-email-stefan.naewe@gmail.com>

Stefan Naewe <stefan.naewe@gmail.com> writes:

Show 5 quoted lines

> mark_tree_uninteresting dereferences a tree pointer before checking
> if the pointer is valid. Fix that by doing the check first.
>
> Signed-off-by: Stefan Naewe <stefan.naewe@gmail.com>
> ---

I still have a problem with "dereferences", as "dereference" is about computing an address and accessing memory based on the result, and only the first half is happening here. I can live with "The function does a pointer arithmetic on 'tree' before it makes sure that 'tree' is not NULL", but in any case, let's queue this as-is for now and wait for a while to see if others can come up with a more appropriate phrases.

Thanks.

Show 21 quoted lines

>  revision.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/revision.c b/revision.c
> index 0fbb684..8c569cc 100644
> --- a/revision.c
> +++ b/revision.c
> @@ -135,10 +135,12 @@ static void mark_tree_contents_uninteresting(struct tree *tree)
>  
>  void mark_tree_uninteresting(struct tree *tree)
>  {
> -	struct object *obj = &tree->object;
> +	struct object *obj;
>  
>  	if (!tree)
>  		return;
> +
> +	obj = &tree->object;
>  	if (obj->flags & UNINTERESTING)
>  		return;
>  	obj->flags |= UNINTERESTING;